The present invention is directed to microwave antennas and finds particular application in printed-circuit or other thin microwave antennas of the type that can be made to conform to the surface of an aircraft.
In place of conventional waveguides, thin devices, commonly referred to as stripline or microstrip devices, have been used, for some time, to conduct microwave signals, and antennas have been fabricated employing this technology. The small size and low weight of such devices make them attractive for aircraft applications. Additionally, since antennas employing this technology can be made to be very thin in one dimension, they can easily be made to conform to the surfaces of aircraft.
However, these thin antennas tend to have considerably narrower bandwidths than do the more conventional waveguide types.
An antenna configuration that significantly reduces this drawback is disclosed in U.S. Pat. No. 4,197,545 to Favaloro et al. In that arrangement, shorting elements extending between ground planes of a stripline structure define a cavity, and one of the ground planes provides a slot opening into the cavity. The feed for this antenna is provided by a T-shaped conductor extending into the cavity and connected to the ground plane at the ends of the crosspiece of the T. It has been found that this type of antenna has a bandwidth that is significantly wider than those possible with previous stripline or microstrip antennas.